The present invention relates to a system for transmitting signals that can be broken down into at least one AC voltage component, between a rotor and a stator, from a sender unit to a receiver unit, with the help of pairs of annular coils, the coil windings of which form parts of the sender or receiver unit and which are arranged coaxially to the axis of rotation of the rotor and which are inductively coupled.
In many technical areas, for example during the analysis process using an ultra-centrifuge as described in DE-PS 29 43 942, it is necessary to transmit electrical signals, which may be in the form of analog or digital values, from a rotor to a stator after suitable intermediate amplification, when they are then displayed or subjected to further processing. On the other hand, in many instances there is a need to transmit control or switching commands from the stator to the rotor by means of electrical signals.
The use of slip-ring systems is already known; however, such systems are associated with difficulties based on matters of principle when the signals that are to be transmitted involve relatively low voltages, and in particular when high rotational speeds of the rotor are involved. In addition, the various magnetic, electrostatic, and light-scanning systems, already known in electro-accoustic technology, also form part of the prior art. Using these, signals are stored on a moveable carrier, for example, an optical disk, by scanning onto a fixed receiver unit.
Generally speaking, during the transmission of the signal, particular difficulty is encountered if one or a plurality of measurement devices rotate with the rotor, and the measured or output values of these, which can be varied in time, are to be transmitted to a fixed receiver unit.
DE-PS 28 46 583 describes an apparatus for transmitting measuring signals through a transmitter from a rotor to a stator, and for transmitting a supply voltage through the same transmitter from the stator to the rotor. This is effected in that there is a power oscillator with a low output impedence on the stator side so as to generate the supply voltage, this having an essentially higher frequency than the frequency modulated measuring signals, the oscillator being connected to the transmitter through a condenser, and in which between the condenser and the transmission coil, the measuring signals are uncoupled at a point that is of a high resistance during transmission conditions, a rectifier for the supply voltage and a signal generator for the measuring signals being arranged on the rotor side, it being possible to couple the measuring signals in a point between the rectifier and the transmission coil. Such a dual exploitation of the coil elements of the transmitter that are figured as annular coils causes problems that are associated with circuit technology.
Also part of the prior art is an arrangement for measuring the temperature on rotating shafts, which is described in DE-PS 958 600. In this, there are two inductive transmitters in conjunction with a bridge circuit, one branch of which incorporates a resistance thermometer. The bridge receives its supply voltage through the annular coil system of one transmitter, whereas the other annular coil system of another transmitter passes on the measured values to the display instrument.